There are many applications for displays that use backlighting technology, in which LEDs are typically used to illuminate or otherwise display information. For example in high-end avionics applications, such displays are present on the instrument panel or console of an aircraft for navigation, system monitoring, or other purposes. There are several considerations when driving such displays.
A first consideration is that a wide dimming range is useful for accommodating very different operating conditions for a display. Generally, dimming is the process of adjusting the intensity of light (illumination) from an LED of the display. As understood by a person skilled in the art, the range of dimming extends from the maximum light output of the display to minimum light output when the display is controlled to its lowest powered level. Examples of the different operating conditions include daytime high-altitude flight where sunlight directly strikes the display through the cockpit window (wherein the illumination by the LED therefore needs to be increased for improved visibility), and vision-enhanced or stealth night-time flight using night vision goggles or other equipment (wherein the illumination of the LED needs to be at a low level to maintain stealth while still providing acceptable visibility).
A second consideration is that consistent color over the dimming range, LED temperature, and LED life should be maintained, so as to provide rapid recognition of visual cues. For instance with some type of LED displays, significant and undesirable color shifting will occur if the amplitude of the current supplied to the LEDs is not precisely controlled with respect to the optical output.
A third consideration is efficiency. Some types of LED displays do not operate efficiently, thereby increasing the load on power supplies, increasing temperature of the display, and reducing the life the LED display.
A fourth consideration is luminance stability. Unwanted flicker, flashing, or luminance changes in a pilot's peripheral vision are undesirable visual distractions.
LED displays using existing backlight technology fail to adequately address the above and/or other considerations.